This invention relates to continuous casting, typically to continuous casting of steel. It has particular relationship to the shielding, by a gas for deoxidation purposes, of the stream of molten metal which flows from the tundish to the mold or from the ladle to the tundish (Cashdollar U.S. Pat. No. 3,754,590). The anti-oxidation gas shields the molten metal in the stream from the oxygen in the air or reacts with the oxygen. Typical deoxidation gases include non-reactive gases which serve for shielding and are the inert gases, such as helium, argon, neon or krypton and such gases as nitrogen. Another practice is to admit natural or artificial gas (methane) into the region to be protected and consuming the oxygen by burning the gas. As used in this application, the expression "anti-oxidation gas" means an inert gas or such gases as nitrogen or any mixture of these gases or gases which absorb the oxygen by reaction.
In accordance with the teachings of the prior art, attempts have been made to use for a shroud a pipe having a polygonal, particularly square, cross-section. This structure has in practice proven useless. Attempts have also been made to provide a shroud in the form of a platform or plate from which there projects a four-sided pyramid, terminating in a square or rectangular opening. This shroud is costly. Its manufacture has high labor cost because it is necessary to form the plates which constitute the sides of the pyramid and then secure them, by welding, to the base plate and to each other to form the pyramid. In addition, in practice this pyramid shroud has been found to be ineffective.
It is an object of this invention to overcome the above disadvantages of the prior art and to provide a shroud which shall effectively shield or otherwise protect from oxidation the metal stream of continuous casting apparatus either between the tundish and the mold or between the ladle and the tundish and shall also be capable of being manufactured at low cost. It is also an object of this invention to provide a method for making such a low-cost shroud.